They write to make this:
In Pins.h (scroll down into the “RAMPS pin assignment” section or the board matching your setup) make sure the following lines are present, if not add them:
#define ORIG_E2_STEP_PIN 64
#define ORIG_E2_DIR_PIN 59
#define ORIG_E2_ENABLE_PIN 44
#define E2_PINS ORIG_E2_STEP_PIN,ORIG_E2_DIR_PIN,ORIG_E2_ENABLE_PIN,
change to ramps pins.h definition as they have a extension board for extra driver.
With that you can use Extruder 2, but you did not add it correct and even worse
different code.